SCR-AE-183
The 1930's bay wouldn't be complete without some representation of the lower power "command" sets - as opposed to the
greater capability BC-224-A and BC-AA-191 "liaison" set described on another page. In the USAAC, that role was served by the SCR-**-183, dating back
to the early 1930s. Some examples of the piece parts going into that set are shown below, this one an "AE" variation from 1935.
ARC designed and produced a similar set for the US Navy (called the RU/GF series), but it had some diverging differences in circuit
design and tube types as the years rolled on. I have almost everything I need on this set except a BC-AE-232 transmitter control box and
an -AA- through -AF- receiver, and would deeply appreciate any leads to finding either one of those. In the meantime a nice BC-AN-229 will
stand in for the real receiver.
BC-AE-230 radio transmitter. "IU" signifies an "Installation Unit" intended for test fitting in various aircraft.for maintenance
clearance, ease of operation, structural support, etc.
ARL stands for the Signal Corps Aircraft Radio Laboratory, the primary aircraft radio communication
engineering facility for the USAAC from the end of WWI
through October 1944, located at Wright Field in Dayton, Ohio. Strangely enough,
the Aircraft Radio Corporation always installed black faced RF ammeters in their transmitters
starting with the first -AA- model. The
next contract after this -AE version, the -AF-, was awarded to Western Electric, in which they inexplicably installed the only white faced meter
in the entire SCR-183 series of -AA- to -AS-.
BC-AE-230 radio transmitter tag
BC-AE-230 radio transmitter side view
BC-AE-231 receiver control box.
BC-AE-198 antenna relay. This one is from the ARC Morgue.
Receiver tuning head MC-125-A with M-185 tuning dial light and BC-326 dial light control box.
Also shown on the left is an MC-135 remote control to change receiver bands remotely.
The wire into the light requires a small nipple to provide strain relief and accommodate the #18 wire
normally used for this kind of current, but this nipple is usually missing and had to be fabricated for this set.
The light is a 3 volt LM-32 (industry 323) that was powered from either a vibrator supply called an "auxiliary box" intended
primarily for the 110 volt cockpit UV lights, or through a dropping resistor in the BC-326 tuning dial switch box.
Not shown are the flexible MC-124 and MC-134 "speedometer" cables on the drawing below, used to tune the receiver or switch bands.
They are covered in some detail here. By the way,
Dave (AB5S) pointed out that with a typical 2-3 foot cable, the MC-135 needs to rotate almost a full 180 degrees either way from top to switch bands
in a dual band coil due to the torque required by the multiple ganged switch. The cable has some torsional "give" to it with anything over 6".
That means you have to plan its location carefully to allow your hand (and the lever) to rotate that much without bumping into something else.
The drawing below shows the wiring diagram for the set using an alternative aircraft junction box (called a connector panel),
intended for a small cockpit like a fighter plane or trainer. This is used in place of the TM-AE-172 junction box that was
originally designed for larger multiplace aircraft, where conduit runs would be longer and the controls would be placed some
distance from the junction box. Later in the war, this use of a custom junction box seems to have become more the norm rather than
using the "official" TM-172, but a lot depends on the point in the war that one is considering. Given the small size of the
1930's bay, it made more sense to use the approach of the fighter version, shown below the schematic. Also note that wire and terminal numbers in this
diagram aren't all correct for an -AE- or -AG- implementation of the junction box, which changes the seven pin PL-104 on the receiving control
box to a six pin PL-65, for example. Subtle differences like this one can cause a lot of hair pulling time in final startup.
SCR-183 junction box (fighter aircraft version) system wiring diagram.
SCR-183 junction box (fighter aircraft version). All the cable lengths are sized to accommodate a physically small installation.
SCR-183 junction box interior (fighter aircraft version).
BD-87-C dynamotor. Note warning tag on the mounting strut.
BC-216 microphone amplifier for dynamic microphone
This last item is actually an add-on to the RC-15A interphone set
that will be a part of the SCR-183 operational system here on the "flight deck". Since the dynamic mics for which it was designed are primarily
throat microphones, the primary use for this preamplifier will actually be to help salvage some of the sensitivity of 1930's era carbon microphones
(like the venerable T-17)
whose carbon granules have become largely cemented to one degree or another over the years. A minor reversible tweak to the jack box is all that is
necessary to provide current for the carbon microphones - that current is not supplied by the BC-216 because dynamic mics don't require it.
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